Insulin dependent diabetic women desiring pregnancy are frequently counseled that pregnancy may worsen chronic complications of diabetes, specifically retinopathy and nephropathy. This project will study the effect of pregnancy on diabetic microvascular disease. It will test the hypothesis that pregnancy in the insulin dependent diabetic increases the progression rate of diabetic microvascular disease and determine whether the pregnant state, per se, or the theraputic measures of diabetic treatment during pregnancy, intensive insulin therapy, result in acceleration of microvascular disease manifested primarily by worsening of diabetic retinopathy. The study will involve two groups of subjects. The first group will be pregnant diabetic women enrolling in the Core Clinical Trial. The second will be a group of non-pregnant diabetic women matched for duration of diabetes and number of previous pregnancies. The latter group will be comprised primarily of women have previously participated in the Core Clinical Trial since 1978. Control subjects will have their diabetes managed in the same fashion, to the same level of glycemic control and for the same duration as their pregnant counterparts. After this period of intensive management, "the pregnant period" in both groups, each pair will be followed for two more years to examine the longer-term effects of pregnancy on diabetic microvascular disease. During the pregnant period, both groups will have detailed eye exams including fundus photography at intervals corresponding to each trimester for the pregnant subject. After pregnancy, both groups will have fluorescein angiography yearly and fundus photography every 4 months. Other pertinent measures will include glycohemoglobin (monthly during pregnancy and every two months in the follow-up period), urinary microalbumin excretion (same schedule as eye exams). Patients will also perform home glucose monitoring using "memory" reflectance meters and have regular physician visits. It is expected that pregnant diabetic patients will show an increase in the progression rate of diabetic retinopathy during pregnancy compared to controls which will be, in part, attributable to intensive insulin therapy. The follow-up period will determine if pregnancy has an independent effect on acceleration of diabetic microvascular disease and will allow health care providers to provide accurate information to diabetic women seeking pregnancy regarding long-term consequences for themselves and their families.